Cherenkov emission, which is generated during radiation therapy, can be utilized for imaging that is synergistic with radiation therapy. Cherenkov light can be utilized to excite phosphors, which then can be imaged utilizing Cherenkov excited luminescence scanned imaging (CELSI). Europium chelate microspheres, which exhibit bright luminescence with long luminescent lifetime, were appended with multiple copies of cetuximab. This will allow for selective imaging of EGFR overexpressing tumors during the course of radiation therapy via CELSI. We have characterized the functionality of the cetuximab loaded microspheres in vitro via ELISA, as well as via fluorescence microscopy in EGFR overexpressing A431 cells. These microspheres were intravenously injected into athymic nude mice bearing A431 flank tumors and allowed to incubate for a series of time points. They were then imaged first via standard fluorescence imaging to determine the ideal time point for visualizing tumors via CELSI. After demonstrating selective accumulation in tumors, imaging was then undertaken in vivo via CELSI. These antibody conjugated europium microspheres provide promise to image tumors selectively with CELSI. Future studies involve conjugating other antibodies to the europium microspheres to utilize in CELSI.

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Jennifer R. Shell, Liberty N. Gendron, Ethan P. LaRochelle, Xu Cao, and Brian W. Pogue, "Tumor targeting cetuximab conjugated europium microspheres for Cherenkov excited luminescence scanned imaging (Conference Presentation)," Proc. SPIE 10862, Molecular-Guided Surgery: Molecules, Devices, and Applications V, 1086217 (Presented at SPIE BiOS: February 04, 2019; Published: 4 March 2019); https://doi.org/10.1117/12.2515383.6008538093001.